Magnetic disk apparatus

Abstract

A magnetic disk apparatus includes a dual head equipped with an MR head for reading data and an inductive head for writing the data. One ID portion and one servo pattern are disposed in one sector and an unequal track pitch is formed. The ID portion is formed at the center of a radius of two positions to which the MR head is positioned at the time of reading the data and writing the data, respectively.

We claim: 
     
       1. A magnetic disk apparatus having a magnetic disk medium, comprising: a dual head for reading or writing information from or to said magnetic disk medium, having at least one gap for effecting magnetic recording and at least one gap for effecting magnetic reproduction set on a slider;   a spindle motor for supporting and rotating said magnetic disk medium;   a head assembly including said dual head, said slider and a support member for supporting said slider;   a carriage arm including a pivot shaft for supporting and moving said head assembly across said magnetic disk medium;   a voice coil motor for driving said carriage arm;   an electronic circuit for causing said magnetic head to read and write information from and to said magnetic disk medium; and   a controller for controlling the operations of said electronic circuit, said spindle motor and said voice coil motor,   wherein said magnetic disk medium has at least one ID information in one unit of information storage in addition to servo information for controlling positioning of said head assembly in one of said plurality of tracks, and wherein said tracks have unequal track pitches, of which a change rate in rotational angle of said carriage arm is not greater than 7% between two adjacent tracks of unequal track pitch.   
     
     
       2. A magnetic disk apparatus having a magnetic disk medium, comprising: a dual head for reading or writing information from or to said magnetic disk medium, having at least one inductive head for effecting magnetic recording and at least one magneto-resistive (MR) head for effecting magnetic reproduction set on a slider;   a spindle motor for supporting and rotating said magnetic disk medium;   a head assembly including said dual head, said slider and a support member for supporting said slider;   a carriage arm including a pivot shaft for supporting and moving said head assembly across said magnetic disk medium;   a voice coil motor for driving said carriage arm;   an electronic circuit for causing said magnetic head to read and write information from and to said magnetic disk medium; and   a controller for controlling the operations of said electronic circuit, said spindle motor and said voice coil motor,   wherein a write radius position of an ID portion is set to an intermediate point between a positioning radius position of said MR head when said MR head reads out data and a positioning radius position of said MR head when said inductive head writes data, and   wherein said magnetic disk medium has at least one ID information in one unit of information storage in addition to servo information for controlling positioning of said head assembly in one of said plurality of tracks, and wherein said tracks have unequal track pitches, of which a change rate in rotational angle of said carriage arm is not greater than 7% between two adjacent tracks of unequal track pitch.   
     
     
       3. A magnetic disk apparatus having a magnetic disk medium, comprising: a dual head for reading or writing information from or to said magnetic disk medium, having at least one gap for effecting magnetic recording and at least one gap for effecting magnetic reproduction set on a slider;   a spindle motor for supporting and rotating said magnetic disk medium;   a head assembly including said dual head, said slider and a support member for supporting said slider;   a carriage arm including a pivot shaft for supporting and moving said head assembly across said magnetic disk medium;   a voice coil motor for driving said carriage arm;   an electronic circuit for causing said magnetic head to read and write information from and to said magnetic disk medium; and   a controller for controlling the operations of said electronic circuit, said spindle motor and said voice coil motor,   wherein said magnetic disk medium has at least one ID information in one unit of information storage in addition to servo information for controlling positioning of said head assembly in one of said plurality of tracks, and wherein said tracks have unequal track pitches, of which a change rate between adjacent tracks of unequal track pitches is not greater than 7%.   
     
     
       4. A magnetic disk apparatus according to claim 3, wherein said dual head includes a read-only MR head and a write-only inductive head, and wherein a core width of said MR head is smaller than that of said inductive head. 
     
     
       5. A magnetic disk apparatus according to claim 3, wherein said dual head includes a read-only MR head and a write-only inductive head, and a gap center of said MR head and a gap center of said inductive head in said dual head are shifted from each other in the direction along their gaps. 
     
     
       6. A magnetic disk apparatus according to claim 3, wherein said track pitches change under a combination of three rates of change of the track pitch. 
     
     
       7. A magnetic disk apparatus having a magnetic disk medium, comprising: a dual head for reading or writing information from or to said magnetic disk medium, having at least one inductive head for effecting magnetic recording and at least one magneto-resistive (MR) head for effecting magnetic reproduction set on a slider;   a spindle motor for supporting and rotating said magnetic disk medium;   a head assembly including said dual head, said slider and a support member for supporting said slider;   a carriage arm including a pivot shaft for supporting and moving said head assembly across said magnetic disk medium;   a voice coil motor for driving said carriage arm;   an electronic circuit for causing said magnetic head to read and write information from and to said magnetic disk medium; and   a controller for controlling the operations of said electronic circuit, said spindle motor and said voice coil motor,   wherein a write radius position of an ID portion is set to an intermediate point between a positioning radius position of said MR head when said MR head reads out data and a positioning radius position of said MR head when said inductive head writes data, and   wherein said magnetic disk medium has at least one ID information in one unit of information storage in addition to servo information for controlling positioning of said head assembly in one of said plurality of tracks, and wherein said tracks have unequal track pitches, of which a change rate between adjacent tracks of unequal track pitches is not greater than 7%.   
     
     
       8. A magnetic disk apparatus according to claim 7, wherein said track pitches change under a combination of three rates of change of the track pitch. 
     
     
       9. A magnetic disk apparatus according to claim 7, wherein a core width of said MR head is smaller than that of said inductive head. 
     
     
       10. A magnetic disk apparatus according to claim 7, wherein a gap center of said MR head and a gap center of said inductive head in said dual head are shifted from each other in the direction along their gaps.